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How Tall are the Highest Mountains on Neutron Stars? – Not as Tall as You Think

Posted by Guy Pirro   09/28/2021 02:11AM

How Tall are the Highest Mountains on Neutron Stars? – Not as Tall as You Think

A neutron star compared with the skyline of Chicago. Neutron stars are about 12 miles in diameter and are extremely dense. Because of their compactness, neutron stars have an enormous gravitational pull -- Around a billion times stronger than the Earth. This squashes every feature on the surface to miniscule dimensions, and means that the stellar remnant is an almost perfect sphere. (Think of a neutron star as giant ball bearing in space, but much, much denser). (Image Credit: Nick Gertonson, Daniel Schwen, Northwestern University, LIGO-Virgo)

 


How Tall are the Highest Mountains on Neutron Stars? – Not as Tall as You Think

When the core of a massive star undergoes gravitational collapse at the end of its life, protons and electrons are literally scrunched together, leaving behind one of nature's most wondrous creations -- a neutron star. Neutron stars cram roughly 1.3 to 2.5 solar masses into a city-sized sphere perhaps 20 kilometers (12 miles) across. Matter is packed so tightly that a sugar cube sized amount of material would weigh more than 1 billion tons, about the same as Mount Everest.

"With neutron stars, we're seeing a combination of strong gravity, powerful magnetic and electric fields, and high velocities. They are laboratories for extreme physics and conditions that we cannot reproduce here on Earth," says Large Area Telescope (LAT) science team member David Thompson of NASA's Goddard Space Flight Center in Greenbelt, Md.

So, if a mountain could form on the surface of a massive neutron star, how tall could it be? That’s the question University of Southampton researchers in the UK have tried to answer… And the answer may surprise you. New models of neutron stars show that their tallest mountains may be only fractions of a millimeter high, due to the huge gravity on these ultra-dense objects.

 

 

 

Neutron stars are some of the densest objects in the Universe. They weigh about as much as the Sun, yet measure only around 10 km across, similar in size to a large city.

Because of their compactness, neutron stars have an enormous gravitational pull around a billion times stronger than the Earth. This squashes every feature on the surface to miniscule dimensions, and means that the stellar remnant is an almost perfect sphere.

While they are billions of times smaller than on Earth, any deformations from a perfect sphere on a neutron star are nevertheless known as mountains. The team behind the work, led by PhD student Fabian Gittins at the University of Southampton, used computational modeling to build realistic neutron stars and subject them to a range of mathematical forces to identify how the mountains are created.

The team also studied the role of the ultra-dense nuclear matter in supporting the mountains, and found that the largest mountains produced were only a fraction of a millimeter tall, one hundred times smaller than previous estimates.

Fabian comments, “For the past two decades, there has been much interest in understanding how large these mountains can be before the crust of the neutron star breaks, and the mountain can no longer be supported.”

 

 

 

Past work has suggested that neutron stars can sustain deviations from a perfect sphere of up to a few parts in one million, implying the mountains could be as large as a few centimeters. These calculations assumed the neutron star was strained in such a way that the crust was close to breaking at every point. However the new models indicate that such conditions are not physically realistic.

Fabian adds, “These results show how neutron stars truly are remarkably spherical objects. Additionally, they suggest that observing gravitational waves from rotating neutron stars may be even more challenging than previously thought.”

Although they are single objects, due to their intense gravitation, spinning neutron stars with slight deformations should produce ripples in the fabric of spacetime known as gravitational waves. Gravitational waves from rotations of single neutron stars have yet to be observed, although future advances in extremely sensitive detectors such as advanced LIGO and Virgo may hold the key to probing these unique objects.

 

 

For more information:

 

https://ras.ac.uk/news-and-press/research-highlights/bugs-life-millimetre-tall-mountains-neutron-stars

 

https://www.nasa.gov/mission_pages/GLAST/science/neutron_stars.html

 

https://media.ligo.northwestern.edu/gallery/neutron-star-over-chicago

 

https://astromart.com/news/show/how-big-is-a-neutron-star-smaller-than-you-think

 

https://astromart.com/news/show/are-neutron-star-mergers-the-key-to-heavy-element-creation

 

https://astromart.com/news/show/when-world-collide-neutron-star-collisions-spray-heavy-elements-throughout-small-galaxies

 

https://astromart.com/news/show/first-time-that-a-cosmic-event-is-observed-optically-and-with-gravitational-waves

 

https://astromart.com/news/show/crab-pulsar-sets-new-record-for-high-energy-photons

 

 

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